As is well known in the art, monitoring communication parameters such as the number of incoming and outgoing calls, holding time and lost calls at a communication terminal is needed to properly manage terminal operations. While the information required for evaluating the operating condition of a communication terminal is available at a switching center to which the lines of the terminal are connected, access to such information may involve long delays. In order to improve efficiency and reduce cost, monitoring devices to automatically observe and record the activity of lines at a communication terminal have been employed. With the line monitoring devices, the condition of the terminal and the communication line traffic may be ascertained in a timely fashion without requiring access to a switching center for information.
U.S. Pat. No. 4,712,230 issued Dec. 8, 1987 to J. E. Rice et al., for example, discloses a programmable monitoring and recording apparatus usable with any desired telephone set up in which an off-hook detector and a line status unit provide line status signals to an indicator panel. The monitoring and recording apparatus is connected in parallel with one or more telephones to record in memory and print out, for each detected call, information such as the number dialed, the time, date and duration of call, the station originating the call, the number of rings, whether destination busy and whether there was voice communication. The recorded information on the operation of the telephone set up permits adjustment and modification that improve telephone service on reviewing the recorded information in a timely manner.
U.S. Pat. No. 4,270,024 issued May 26, 1981 to P. Theis et al. discloses a telephone line activity monitor that utilizes a dedicated computer to tabulate line traffic parameters. The monitor computer is adapted to store and display preselected parameters as histograms and to discriminate between incoming and outgoing calls based on the presence or absence of a ring prior to a line going off-hook. Ringing is recognized by measuring the frequency of major fluctuations in the signal on the T-R pair of a telephone line.
Neither of the foregoing automatic monitoring arrangements that acquire information from the lines of a communication terminal detects or determines incoming calls to a communication terminal that are lost due to all lines of the terminal being in a busy state. Such lost calls are blocked at a switching center which may be remotely located in a telephone central office. As a result, there is no indication of the blocked calls on the lines of the communication terminal. Such information on blocked calls may be obtained from the connected switching center by manual inquiry or through the use of relatively expensive and complex circuit connections.
Soviet Union patent Document 1192162 dated Nov. 15, 1982 discloses switching apparatus that monitors lost telephone calls by measuring the number of calls being serviced on every occasion when a call loss is determined. The loss criterion is calculated at the end of a prescribed time interval as a function of the number of calls at the time of each call loss and the number of call losses. The arrangement provides automatic monitoring of the condition of a system and measurement of the statistical characteristics of telephone call transmission. Accuracy is improved by taking into account all calls in analysis. The monitoring requires detection of lost calls. As aforementioned, such lost call information is available at switching centers but cannot be obtained by monitoring telephone lines.
Thus, it is a problem of communication terminal management that blocked call information is not available in a timely fashion and that blocked call information is not available through automatic monitoring of communication terminal lines.